Latitude and Longitude

The surface of the Earth is divided into a grid system of two sets of reference lines. Lines running east-west are called lines of latitude or parallels; those running north-south are called lines of longitude, or meridians. The intersection of latitude and longitude lines describes any point on the Earth’s surface. Latitude and longitude are obtained from the angle of lines passing through poles and the Earth’s center. Latitude and longitude are measured in degrees (°), minutes (‘), and seconds (“). One degree (1°) = 60 minutes. One minute = 60 seconds. Therefore a point on Earth would be as 98° 45′ 30″ West Longitude, 42° 30’ 15” South Latitude.

Latitude is measured from a 0° reference line that divides the Earth into a northern and a southern hemisphere. The 0° line of latitude is called the equator. Since lines of latitude run east-west, they will be measured from 0° (the equator) to 90° (the poles) in degrees either north or south of the equator.

Longitude is measured from a 0° reference line that passes through Greenwich, England. The 0° line of longitude is called the Prime Meridian. On the opposite side of the Earth, from 0° longitude, will be the 180° line of longitude, called the International Date Line. The Prime Meridian and the International Date Line divide the Earth into the western and eastern hemispheres. Because longitude lines run north-south, they will be measured in degrees either east or west of the Prime Meridian, from 0° to 180°. Since North America is north of the equator and west of the Prime Meridian, all lines of latitude in the continental U.S. are north, and all lines of longitude are west.